Effects of Thermal Shocks on Drifting Aquatic Insects: A Laboratory Simulation
Effects of temperature shocks from thermal plumes on drifting Isonychia (Ephemeroptera: Baetidae) and Hydropsyche (Trichoptera: Hydropsychidae) larvae were examined in a laboratory simulation. Groups of both insects were collected at various seasons and acclimated in the laboratory at temperatures comparable to those in the field. Groups were exposed to thermal shocks of varying duration and observed for periods of 10 days afterward. Consistent statistically significant differences in mortality between treatment and control groups were not evident until shock temperatures neared the respective upper lethal limits for the two insects. While consistent treatment related differences in molting frequency in Isonychia were not obtained, changes in the patterns of molting were observed. Behavioral tests with Isonychia indicated no discernable treatment effects on rheotaxis, phototaxis, and substrate orientation. No discernable effects of treatment on susceptibility to predation of Isonychia by Cottus carolinae were observed.